Mimecast Gateway Policies are a set of rules, applied to either Inbound or Outbound messages, that affect the email traffic flow. They allow Administrators to apply granular control to email messages processed by Mimecast. For example they can:

A number of default policies are provided with each Mimecast installation, with the available policies being dependent on the Mimecast products purchased. As there are policies for specific pieces of Mimecast functionality, each policy is listed by it's Policy Type (e.g. Blocked Senders, Stationery).

Whilst some Policy Types are applied directly with on / off functionality, others (e.g. Targeted Threat Protection - Attachment Protect) work with Definitions. These allow Administrators to configure more specific settings for an even more granular level of control.

Policies can be created to be active straight away, or for a time period in the future. If the policy is active, any changes made to it take effect as soon as it is saved. However it can take up to five minutes for the change to propagate through your email messages.